The following video shows how a car tent was used as an artificial barrier denying entrance to a hall.
After hours of trying to glitch through somehow I finally managed to do so, by driving up my car backwards to the tent and attempting to somehow jump on top of it through the small slit between tent and door frame.
Another car tent was used to deny access to the other entrance of this hall (not shown in video). There it would simply not show the "open" option for the door as the tent was overlapping the door from the inside.
I have labelled this as "Major" because bases are, for everything I've heard from Peter Nespesny, never designed to be unbreakable/unenterable. Feel free of course to correct this labelization if deemed incorrect.